The present invention relates to medical leads generally and more particularly to implantable cardiac pacing leads.
In the context of permanently implantable cardiac pacing leads, the pacing electrodes mounted to the leads have typically taken the form of a solid metal electrode body coupled to a separately formed coiled metal conductor. For example, as disclosed in U.S. Pat. No. 3,348,548 issued to Chardack and U.S. Pat. No. 5,282,844 issued to Stokes. More recently, there has been a renewed interest in cabled or stranded conductors in the context of cardiac pacing leads, for example as disclosed in U.S. Pat. No. 5,584,873 issued to Shoberg et al. and U.S. Pat. No. 5,246,014 issued to Williams et al.
In the early days of pacing, it was proposed that pacing electrodes could take the form of a continuation of the conductor within the pacing lead body. For example, U.S. Pat. No. 3,804,098 issued to Friedman employs an extension of a tinsel wire conductor as a pacing electrode. Alternatively, a stranded wire, exposed to the distal end of the lead and filled with silver has been proposed as a pacing electrode in U.S. Pat. No. 3,731,376 issued to Ackerman. Simply extending an uninsulated portion of a coiled or stranded conductor to serve as an electrode is disclosed in U.S. Pat. No. 3,416,533 issued to Fisher et al and U.S. Pat. No. 3,035,583 issued to Hirsch et al., respectively. Extending a braided carbon fiber conductor to serve as a pacing or defibrillation electrode is disclosed in British Patent No. 1,219,017 issued to Thompson-Telco and U.S. Pat. No. 5.336,254 issued to Brennen et al., respectively.